This is a pretty clever use of the blockchain. However, instead of destroying the bitcoins you have (wasting coins is bad, no matter how small) you can simply s

This is a pretty clever use of the blockchain. However, instead of destroying the bitcoins you have (wasting coins is bad, no matter how small) you can simply send bitcoins to yourself and store data in the `coinbase` field. The resulting transaction will appear in the blockchain permanently, and can always be referred back to. There already exists a service to prove the existence of a document before a certain date (much like the one in the blog post): http://www.proofofexistence.com/ http://www.proofofexistence.com/ Their implementation details are lacking but it should still be clear enough to get an overview. (Edit: I seem to have missed this link in the blogpost) Besides hosting checksums, other types of data have been found in the blockchain, such as some Wikileaks content (http://www.thebitcointrader.com/2013/04/25mb-of-wikileaks-cables-embedded-in.html http://www.thebitcointrader.com/2013/04/25mb-of-wikileaks-ca...) and even links to child porn (http://www.btcpedia.com/ped0-links-in-bitcoin-blockchain/ http://www.btcpedia.com/ped0-links-in-bitcoin-blockchain/).